#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>
int main()
{
    int i, n, sum = 0, result = 0;
    scanf("%d", &n);
    /********** Begin *********/
    i = 1;
    while (i <= n)
    {
        sum += i;
        result += sum;
        i++;
    }
    printf("sum=%d", result);
    /********** End **********/
    return 0;
}